Chemical and electrical excitability are basic characteristics of vertebrate CNS neurons and are responsible for the complex interactive processes required for normal CNS function. In the present proposal, a competing continuation, several important questions relating to the mechanisms of chemical and electrical excitability in mammalian CNS neurons will be addressed, with the intent of obtaining information basic to an understanding of CNS neuronal function. The overall goal of the research is to characterize the cellular, ionic and molecular mechanisms that underlie chemical and sequence in expression of these mechanisms during neuronal differentiation. Voltage-sensitive, ion-sensitive and transmitter activated conductances will be examined. The transmitter of interest is norepinephrine, a transmitter that has been linked to function will also be investigated. The experimental model is an identified CNS neuronal type, the Purkinje neuron of the cerebellum. This CNS neuronal type offers several advantages as an experimental model, including the fact that electrophysiological recordings can be made in both the somatic and dendritic regions. The experimental preparation, modified organotypic cultures of fetal rat cerebellum, offers considerable technical and anatomical advantage of electrophysiological studies of mature and developing neurons. Four types of electrophysiological recording voltage clamp and single channel, to provide information at the cellular, membrane and molecular levels. The use of patch type of recording electrode and associated technology will make it possible to record from both the somatic and dendritic regions, and to manipulate the cellular biochemistry (ie, second messenger systems) during the recording period. Generally accepted experimental approaches will be used. The proposed experiments will provide in-depth information on the physiology of vertebrate CNS neurons and the stages in expression of mature function during neuronal development. Such information is basic to an understanding of CNS neuronal function and development under normal conditions and alterations in function that occur in the diseased state.